1. Field of the Invention
This invention relates to a gasification method and a device for implementing the method. The method consists of metered infeed of fuel, gasification in a reactor, quenching in a quencher, and gas scrubbing, to produce gases containing CO and H2 by partial oxidation of dust-like fuels containing ash with a gasification medium containing free oxygen, at high temperatures and elevated pressure.
To achieve long operating times, the pressurized jacket of the gasification reactor has to be protected reliably against the action of crude gas and against the high gasification temperatures of 1200-1900° C. This is done by confining the reaction or gasification chamber with a cooled tubular shield that is hung in the pressurized jacket. The annular gap between tubular shield and pressurized jacket is flushed.
The fuel is fed to the head of the reactor in pulverized form through burners, using a pneumatic system by the flow transport principle. The crude gas leaves the gasification chamber together with the liquefied slag at the bottom of the reactor and is then cooled to a saturated state by injecting water, and is then freed of entrained fines. The scrubbed crude gas is then fed to further treatment steps.
2. The Prior Art
The autothermic entrained flow gasification of solid, liquid, and gaseous fuels has been known in the technology of gas production for years. The ratio of fuel to gasification medium containing oxygen is chosen so that higher carbon compounds are completely cracked for reasons of synthesis gas quality into synthesis gas components such as CO and H2, and the inorganic components are discharged as molten slag; see J. Carl, P. Fritz, NOELL-KONVERSIONSVERFAHREN, EF-Verlag fur Energie- und Umwelttechnik GmbH, 1996, p. 33 and p. 73.
According to various systems used in the industry, gasification gas and molten slag can be discharged separately or together from the reaction chamber of the gasification device, as shown in German Patent No. DE 197 131 A1. Either systems with refractory linings or cooled systems are used for the internal confinement of the reaction chamber structure of the gasification system; see German Patent No. DE 4446 803 A1.
European Patent No. EP 0677 567 B1 and PCT Publication No. WO 96/17904 show a method in which the gasification chamber is confined by a refractory lining. This has the drawback that the refractory masonry is loosened by the liquid slag formed during gasification, which leads to rapid wear and bigh repair costs. This wear process increases with increasing ash content. Thus, such gasification systems have a limited service life before replacing the lining. Also, the gasification temperature and the ash content of the fuel are limited. Feeding in the fuel as a coal-water slurry causes considerable losses of efficiency—see C. Higman and M. van der Burgt, “Gasification”, Verlag ELSEVIER, USA, 2003. A quenching or cooling system is also described in which the hot gasification gas and the liquid slag are carried off together through a conduit that begins at the bottom of the reaction chamber, and are fed into a water bath. This joint discharge of gasification gas and slag can lead to plugging of the conduit and thus to limitation of availability.
German Patent No. DE 3534015 A1 shows a method in which the gasification media, powdered coal and oxidizing medium containing oxygen, are introduced into the reaction chamber through multiple burners in such a way that the flames are mutually deflected. The gasification gas loaded with powdered dust flows upward and the slag flows downward into a slag-cooling system. As a rule, there is a device above the gasification chamber for indirect cooling utilizing the waste heat. However, there is the danger of plugging and/or erosion of the pipe system from the entrained dust. By separating the gasification gas and the slag, there is the danger of unwanted cooling of the slag and thus likewise the danger of plugging.
Chinese Patent No. CN 200 4200 200 7.1 describes a “Solid Pulverized Fuel Gasifier”, in which the powdered coal is fed in pneumatically and gasification gas and liquefied slag are introduced into a water bath through a central pipe for further cooling. This central discharge in the central pipe mentioned is susceptible to plugging that interferes with the overall operation, and reduces the availability of the entire system.